The present invention relates to a device for extracting solid material on the bed of a body of water, the device being of a type comprising:
an assembly for collecting material on the bed of a body of water;
a riser for lifting the solid material up towards a surface facility;
a pump capable of pumping a liquid, designed for lifting the solid material collected by the collection assembly in the riser towards the surface facility, the pump having an intake inlet and a delivery outlet.
Such a device is for example intended for use in seabed mining operations, or in seabed earth moving and earthworks in view of the installation and establishment of oil production facilities.
The solid material collected from the bed of the body of water consists for example formed of rocks and/or of sediments.
A device of the aforementioned type is known from the document FR-A-2 467 283. This device comprises a surface facility carried by a vessel and an assembly for the seabed. The seabed assembly includes an assembly for the collection of material consisting of an excavator vehicle.
In this device, the solid material collected from the bed of the body of water is conveyed to the surface by means of a pneumatic elevator system. To this end, an air pipeline is tapped into the riser for injecting air into the riser column.
The pneumatic system may be substituted by a pumping system using a pump which drives the stream of liquid loaded with solid material towards the top.
Alternatively, a discontinuous elevator system for pumping seawater has been mentioned, but is not described in detail.
The first system requires an injection of gas into the middle part of the riser. Such a system is thus not always easy to implement. It is in particular necessary to separate at the surface the gas injected into the liquid stream containing the solid material in order to recover the solid material.
The second solution requires the pumping of the collection stream containing the solid material by means of a pump.
Such a solution does not prove to be entirely satisfactory. Indeed, the passage of solid material through the pump causes premature wear and tear of the pump components that come in contact with the solid material.
It is therefore necessary to frequently replace the pump or its components, which requires operations that are complicated at depth, or even an interruption of the production process.
An object of the invention is to obtain a device that enables the collection and recovery of solid material on the bed of a body of water that is very reliable, while at the same time allowing for the continual production of material.
Another goal of the invention is to provide and convey a material having an improved flow, thereby minimising the internal wear of the pipe carrying it.
Yet another goal of the invention is to provide a pumping station for pumping the material that is easily accessible.